I am looking for a rubber material with good durability but a relatively low durometer. Lower than 50 but more than whatever a bicycle inner tube is. Durometer is the un-stretchiness of rubber, the higher the number, the more rigid. Most commercially available rubber is around 50 or higher. The purpose is to create a forefoot-protector for high-speed reps on the track. At faster speeds, the friction literally tears off chunks of skin, bringing a workout to a gory end after 1 or 2 repeats. I posted about this problem a while back. I solved the problem, mostly, using a loop of elastic fabric with shoe leather sewn on the outside edge of the forefoot. But it's a bit bulky and unwieldy, and leaves unprotected gaps that still get torn to bits by the friction, limiting me to about 2000 meters max of speed work on a good day. An older prototype made of bicycle tube rubber was more protective, but ripped too easily. Vibram rubber is, I expect, durable enough, but I don't know how stretchy it is and it's relatively expensive. Since many of you have the stuff on your minimalist shoes, maybe you can tell me. Also how thick is it? Thinner the better, as far as price. If I can invent a completely effective device, then I'll describe the design in another post.